The process of dynamic deformation of shock-loaded cylindrical "porous" samples of lead, tungsten, and the 95% W + 3.5% Ni + 1.5% Fe alloy consisting of particles 0.1-2.5 mm in size is considered. The shock-wave intensity was slightly lower than the values corresponding to complete compaction of the material. The influence of the particle size and material strength and plasticity on the processes considered is examined.In solving a number of applied problems associated, e.g., with acceleration of cylindrical shells by the energy of an explosion, one has to predict the characteristics of this process. The problem becomes much more complicated if the shell material loses its compactness during acceleration. The reasons for the loss of compactness can be spalling of the shell, its fragmentation by shear stresses, or the loss of stability in the course of shell implosion [1-3]. To correctly calculate the shell motion in such a state, one has to know the behavior of the fragmented material under dynamic compression. A medium with discontinuities is called a damaged, fragmented, or porous medium. Examples of such media are sand, crushed stone, chips, sintered powders, various foam-based materials, and ceramics. Investigation of their behavior under dynamic compression, especially in the range of pressures corresponding to their complete compaction, is of independent interest. It should be noted that development of reliable models of deformation of such materials is hindered by the lack of experimental data on their behavior under dynamic compression. This particularly refers to materials with a wide range of characteristic particle sizes (from tens of micrometers to several millimeters).In the range of comparatively low pressures, particles of materials under consideration under dynamic or shock-wave loading are first loaded by the shock wave (SW) and then are unloaded to surrounding pores. Because of the finite volume of the "porous" space, the particles experience several circulations of compression and rarefaction waves. This leads to formation of a transitional zone between the SW front and the region of final states; the width of this zone is determined by the time of decay of compression and rarefaction waves circulating in the particles or the time of pore implosion and by the thermal relaxation of particles [4]. When the oscillations decay, the SW propagates in a steady mode; dissipation of kinetic energy of the particle material in the shock-transition zone results in an increase in the thermal component of internal energy and in enhanced shock-induced heating of the porous material. In addition to these features, sintered powders, foam-based materials, and ceramics whose particles are connected by a skeleton have additional peculiarities caused by skeleton compression or breakdown. For this reason, the behavior of a porous or fragmented material under shock-wave compression can be characterized by propagation of complicated multi-wave structures consisting of one or several elastic precursors and a wave of ir...

No abstract

No abstract

No abstract

An innovative approach is proposed to increase the useful life of assembled cutting tools by designing a special shape of the flank surface of indexable faceted cutting inserts (IFCIs). Calculation relationships were developed as a way to define the nature and degree of effect of blade geometry on the flank wear rate. The paper describes specifics of designing the optimal flank shape for roughing and finishing operations. Curved (convex) flank geometry is confirmed to effectively increase the tool life before reaching the maximum allowed flank wear land. An important factor for choosing the insert flank geometry and dimensions is the strength of the cutting blade of the insert. To maximize tool life with regard to the insert strength, a CAD method is developed for geometry calculation and optimization of the complex-profile flank surface. IFCI design examples featuring modified flank geometry offer improved tool life. Complex flank shape comprising a series of elementary surfaces with different geometry, is shown to be highly efficient. The results of field tests for new IFCIs in milling operations confirm the great practical value of methods for controlling the tool wear behavior through modified flank geometry.